A method of processing geological data comprising a plurality of geological surfaces within a geological volume is provided. The method includes the steps of: (i) specifying a well trajectory which extends through the geological volume; (ii) identifying the geological surfaces within the volume which are intersected by the trajectory; (iii) determining, for each intersected surface, the depth, the dip angle and the dip direction of the surface at the point of intersection with the trajectory; and (iv) predicting a well log for the trajectory, the log specifying the depths, dip angles and dip directions of the intersected geological surfaces.